3D imaging techniques for characterising microcracks in cement-based materials

• Published in: Cement and concrete research 2021-02, Vol.140, p.106309, Article 106309
• Main Authors: Mac, M.J., Yio, M.H.N., Desbois, G., Casanova, I., Wong, H.S., Buenfeld, N.R.
• Format: Article
• Language: English
• Subjects: 3D imaging; Cement paste; Concrete (E); Durability (C); Freeze thaw cycles; Image analysis (B); Imaging techniques; Ion beams; Laser beams; Mechanical properties; Microcracking (B); Microcracks; Microstructure (B); Mortars (material); Shrinkage; Three dimensional imaging; Tomography; X ray microtomography
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2020.106309

Concrete inherently contains pores and microcracks that can adversely impact its mechanical properties and long-term durability. However, characterising microcracks is difficult due to their complex, multiscale and three-dimensional (3D) nature. This paper presents an evaluation of 3D imaging techniques for characterising microcracks induced by different mechanisms. Seven cement pastes, mortars and concretes subjected to drying shrinkage, autogenous shrinkage and freeze-thaw cycles were investigated using focused ion beam nanotomography (FIB-nt), broad ion beam serial section tomography (BIB-SST), laser scanning confocal microscopy (LSCM) combined with serial sectioning and X-ray microtomography (μCT). The study shows that the characteristics of microcracks vary significantly depending on exposure conditions. Yet there is no single technique that can capture the entire size range of microcracks from sub to tens of μm within a sufficiently representative sampling volume. The achievable image volume and resolution, and the advantages and disadvantages of each technique are compared and discussed.